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Suppose that f is a projective birational morphism with at most one-dimensional fibres between d-dimensional varieties X and Y, satisfying ${\bf R}f_* \mathcal{O}_X = \mathcal{O}_Y$. Consider the locus L in Y over which f is not an…

Algebraic Geometry · Mathematics 2018-10-30 Will Donovan , Michael Wemyss

Dilation theory is a paradigm for studying operators by way of exhibiting an operator as a compression of another operator which is in some sense well behaved. For example, every contraction can be dilated to (i.e., is a compression of) a…

Operator Algebras · Mathematics 2020-02-18 Orr Shalit

The central objective of this article is to investigate such isometric covariant representations that serve as dilations of completely contractive covariant representations.

Operator Algebras · Mathematics 2025-09-05 Azad Rohilla , Dimple Saini

In this work we study what we call Siegel--dissipative vector of commuting operators $(A_1,\ldots, A_{d+1})$ on a Hilbert space $\mathcal H$ and we obtain a von Neumann type inequality which involves the Drury--Arveson space $DA$ on the…

Functional Analysis · Mathematics 2021-09-10 Nicola Arcozzi , Nikolaos Chalmoukis , Alessandro Monguzzi , Marco M. Peloso , M. Salvatori

We consider non-commutative deformations of sheaves on algebraic varieties. We develop some tools to determine parameter algebras of versal non-commutative deformations for partial simple collections and the structure sheaves of smooth…

Algebraic Geometry · Mathematics 2021-08-31 Yujiro Kawamata

This paper concerns a commutant lifting theorem and a Nevanlinna-Pick type interpolation result in the setting of multipliers from vector-valued Drury-Arveson space to a large class of vector-valued reproducing kernel Hilbert spaces over…

Functional Analysis · Mathematics 2019-12-04 Deepak K. D. , Deepak Pradhan , Jaydeb Sarkar , Dan Timotin

In this paper we develop the method of double operator integrals to prove trace formulae for functions of contractions, dissipative operators, unitary operators and self-adjoint operators. To establish the absolute continuity of spectral…

Functional Analysis · Mathematics 2018-03-01 Mark Malamud , Hagen Neidhardt , Vladimir Peller

The principal theorem of Sz.-Nagy on dilation of a positive definite Hilbert space operator valued function has played a central role in the development of the non-self-adjoint operator theory. In this paper we introduce the positive…

Functional Analysis · Mathematics 2015-04-30 Dumitru Gaşpar , Păstorel Gaşpar , Nicolae Lupa

A classical result of Sz.-Nagy asserts that a Hilbert space contraction operator $T$ can be dilated to a unitary $\cU$. A more general multivariable setting for these ideas is the setup where (i) the unit disk is replaced by a domain…

Functional Analysis · Mathematics 2022-07-08 Joseph A. Ball , Haripada Sau

We prove several noncommutative maximal inequalities associated with convex functions, including a Doob type inequality for a convex function of maximal operators on noncommutative martingales, noncommutative Dunford-Schwartz and Stein…

Operator Algebras · Mathematics 2014-12-31 Turdebek N. Bekjan , Zeqian Chen , Adam Osȩkowski

Rudin's version of the classical Julia-Wolff-Carath\'eodory theorem is a cornerstone of holomorphic function theory in the unit ball of $\mathbb{C}^d$. In this paper we obtain a complete generalization of Rudin's theorem for a holomorphic…

Complex Variables · Mathematics 2025-09-18 Leandro Arosio , Matteo Fiacchi

Consider a_1,a_2,...,a_n, arbitrary elements of R. We characterize those real functions f that decompose into the sum of a_j-periodic functions, i.e., f=f_1+...+f_n with D_{a_j}f(x):=f(x+a_j)-f(x)=0. We show that f has such a decomposition…

Classical Analysis and ODEs · Mathematics 2007-05-25 Bálint Farkas , Viktor Harangi , Tamás Keleti , Szilárd Gy. Révész

We give necessary and sufficient conditions for stratification and costratification to descend along a coproduct preserving, tensor-exact $R$-linear functor between $R$-linear tensor-triangulated categories which are rigidly-compactly…

Category Theory · Mathematics 2022-05-12 Liran Shaul , Jordan Williamson

The class of Schur-Agler functions over a domain ${\mathcal D} \subset {\mathbb C}^{d}$ is defined as the class of holomorphic operator-valued functions on ${\mathcal D}$ for which a certain von Neumann inequality is satisfied when a…

Functional Analysis · Mathematics 2007-05-23 Joseph A. Ball , Vladimir Bolotnikov

We introduce the notion of characteristic functions for commuting tuples of hypercontractions on Hilbert spaces, as a generalization of the notion of Sz.-Nagy and Foias characteristic functions of contractions. We present an explicit method…

Functional Analysis · Mathematics 2019-05-22 Monojit Bhattacharjee , B. Krishna Das , Jaydeb Sarkar

In this paper, we establish a multi-parameter version of Bellow and Losert's Wiener-Wintner type ergodic theorem for dynamical systems not necessarily being commutative. More precisely, we introduce a weight class $\mathcal{D}$, which is…

Operator Algebras · Mathematics 2016-02-03 Guixiang Hong , Mu Sun

We present some general theorems about operator algebras that are algebras of functions on sets, including theories of local algebras, residually finite dimensional operator algebras and algebras that can be represented as the scalar…

Operator Algebras · Mathematics 2009-07-30 Meghna Mittal , Vern Paulsen

We study the interaction between unitary $\rho$-dilations of a pair of Hilbert space operators and Birkhoff-James orthogonality. We prove that for two orthogonal operators $T,A$ if $\|T\|=\rho$, then $U_T \perp_B U_A$ for any unitary…

Functional Analysis · Mathematics 2023-06-22 Sourav Pal , Saikat Roy

Suppose that $n\geq 1$ and that, for all $i$ and $j$ with $1\leq i,j\leq n$ and $i\neq j$, $z_{ij}\in{\mathbb T}$ are given such that $z_{ji}=\overline{z}_{ij}$ for all $i\neq j$. If $V_1,\dotsc, V_n$ are isometries on a Hilbert space such…

Operator Algebras · Mathematics 2023-05-31 Marcel de Jeu , Paulo R. Pinto

In this paper, applications of the connection between the soliton theory and the commuting nonselfadjoint operator theory, established by M.S. Liv\v{s}ic and Y. Avishai, are considered. An approach to the inverse scattering problem and to…

Functional Analysis · Mathematics 2019-09-24 Galina S. Borisova